1. Probably not (unless you count the DVD set that's out)
2. Maybe we'll find out, but to my knowledge...fan fiction is about all you could look for.
3. Because she is the only one that probably could still/want to do it (and one of the other "ladies" died in Crusade)
4. It just sets up some background really. He loves looking for artifacts and making sure they're put in museums for everyone to see.
5. It's based on several "cults" and "religions," and I believe there were things like this (maybe not shankara stones), but it is loosely based on several things...

Your best bet for this is to buy the DVD set, and watch the movies again, and then watch the bonus features for more info.

P.S. Next time, instead of making it one massive paragraph...make it listed like you did in your edit, so no one misunderstands you.